Java Math.random() method

The java.lang.Math.random() is used to return a pseudorandom double type number greater than or equal to 0.0 and less than 1.0. The default random number always generated between 0 and 1.

If you want to specific range of values, you have to multiply the returned value with the magnitude of the range. For example, if you want to get the random number between 0 to 20, the resultant address has to be multiplied by 20 to get the desired result.

Syntax

Return

It returns a pseudorandom double value greater than or equal to 0.0 and less than 1.0.

Example 1

public class RandomExample1
{
    public static void main(String[] args) 
    {
        // generate random number
        double a = Math.random();
        double b = Math.random();
        // Output is different every time this code is executed  
        System.out.println(a);
        System.out.println(b);
    }
}

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Output:

0.2594036953954201
0.08875674000436018

Example 2

public class RandomExample2
{
    public static void main(String[] args) 
    {
        // Generate random number between 0 to 20
        double a = Math.random() * 20;
        double b = Math.random() * 20;
        // Output is different every time this code is executed  
        System.out.println(a);
        System.out.println(b);
    }
}

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Output:

19.09244621979338
14.762266967495655

Example 3

public class RandomExample3
{
    public static void main(String[] args) 
    {
        // Generate random number between 5 to 30
        double a = 5 + (Math.random() * 30);
        double b = 5 +  (Math.random() * 30);
        // Output is different every time this code is executed  
        System.out.println(a);
        System.out.println(b);
    }
}

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Output: